CD4+ T-cell and monocyte interdependence during discordant xenoimmune responses.
This study was designed to examine our hypothesis that human monocytes provide missing constimulatory signals to host CD4+ cells during interactions with porcine endothelial cells (PECs). PECs were isolated from the aorta. Human CD4+ T cells and monocytes were purified from peripheral blood mononuclear cells (PBMCs). A xenogeneic mixed lymphocyte-PEC reaction (xMLER) was performed to determine the proliferation of PBMCs or CD4+ cells in response to PEC. Monocyte-PEC cocultures with or without CD4+ cells were followed by analysis using fluorescence-activated cell scanning (FACS). We evaluated the CD4+ cells proliferation induced by PEC-conditioned monocytes with or without costimulation blockade. xMLER demonstrated strong lymphocyte proliferation in response to PECs. However, purified CD4+ cells showed reduced proliferative responses to PECs when compared with PBMCs. FACS analysis found that CD14+ monocytes up-regulated CD40 and CD80 expressions in the presence of CD4+ cells. PEC-activated but not resting monocytes induced CD4+-cell proliferation, which was inhibited by anti-CD154, anti-CD80, or anti-CD86 antibodies. In summary, human monocytes exposed to PECs are conditioned to up-regulate costimulatory molecules upon exposure to T cells. PEC-conditioned monocytes induced T-cell proliferation by indirect presentation. Costimulation blockade inhibited T-cell proliferation induced by PEC-conditioned monocytes. Our findings suggested that monocytes play an important role in indirect xenoantigen presentation, providing costimulation to T cells. This interaction can occur distant from the initial site of xenoantigen, but monocytes remaide void of costimulatory signals until their interaction with T cells.
Fang
Y
Y
Department of Transplantation, Jinan City Central Hospital, PR China.
Liu
Z
Z
Zhu
L
L
Wang
P
P
Wang
Y
Y
Xu
H
H
D000818:Animals; D000911:Antibodies, Monoclonal; D001011:Aorta / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000637:transplantation*; D004730:Endothelium, Vascular / Q000276:immunology*; D005434:Flow Cytometry; D006801:Humans; D008213:Lymphocyte Activation / Q000276:immunology; D007959:Lymphocyte Culture Test, Mixed; D009000:Monocytes / Q000276:immunology* / Q000637:transplantation*; D013552:Swine; D014183:Transplantation, Heterologous / Q000276:immunology*
D000911:Antibodies, Monoclonal